The present invention relates to the field of stringed musical instruments of the guitar and bass guitar family, and more particularly it relates to improvements in the structure of frets, Fret Rods (copyright), and associated mounting provisions in the neck/fingerboard.
Typically a stringed instrument has a neck portion of which one side, herein assumed to be facing upwardly, provides a playing surface known as a fingerboard, above which stretched strings are closely positioned so that a player can set the pitch of a string to a desired note by finger-pressing the string against the fingerboard surface at a corresponding position, thus presetting the length of the vibrating portion of the string and accordingly presetting the frequency of the note then played.
The fingerboard may be made integrally with the neck, typically made of hardwood, or it may be made from a different hardwood or other material and laminated onto the neck. The fingerboard surface may be substantially flat or slightly convex-shaped in cross-section.
Typically fingerboards of instruments in the violin family are made fretless while fingerboards of instruments in the lute family, which includes guitars and bass guitars, are usually fitted with a set of transverse metal frets spaced to provide semitone pitch intervals along the fingerboard. A fingerboard fitted with frets is known as a fretboard.
Usually, the fretboard is finger-stopped with the left hand while the right hand picks, strums and/or plucks the strings; however a special member of the lute family, known as a Stick (R) fretboard tapping instrument, is intended to be played with a technique created by the present inventor in which both hands address the fretboard from opposite sides with all eight fingers oriented at right angles to the fretboard, initiating each note by tapping a string against a fret and holding it there for the desired note duration.
In the lute family, generally, apart from open string notes, the pitch of each note played is set by a string being pressed against the upward extremity, i.e. the fret tip, of a selected fret.
The structure of frets and the system by which they are fastened to the neck/fingerboard to form a fretboard are critical with regard to at least seven parameters:
(1) the actual performance of music, related to fret tip shape and overall uniform accurate alignment of the fret tips in a flat plane close to the strings;
(2) the feel of the instrument to the player, particularly to the fingers: the particular cross-sectional shape of the exposed portion of the frets above the fretboard can be felt by the player""s fingers as they move along the strings past the frets in forming notes and expressive nuances, and thus this shape contributes strongly to the overall xe2x80x9cfeelxe2x80x9d of the instrument, which is of great importance to the player;
(3) the aesthetics and general appearance of the instrument;
(4) the producibility including the relative difficulty of assembly and more particularly the effort and time required to level the frets and dress them individually to a satisfactory level of quality;
(5) the long term reliability, including stability and durability, e.g. retention of the frets properly in place over a period of years, and wear along the fret tips;
(6) the maintainability, including the capability and ease of field refurbishment, adjustment and/or replacement of the frets; and
(7) overall cost to produce.
FIGS. 1A-1H show a cross-section of a portion of a neck/fingerboard 10 of a stringed musical instrument fitted with frets of known art having various cross-sectional shapes.
FIG. 1A shows a fret 12A configured with a widely-used conventional cross-sectional shape found in a great majority of known art. This generally T-shaped cross-sectional shape provides a mounting tine extending downwardly by which the fret 12A is retained in a mounting channel with parallel sidewalls sawed transversely across the neck/fingerboard 10. In original assembly or replacement, the fret 12A is hammered into place, forcing the tine downwardly into the channel between the parallel vertical sidewalls. Typically the tine is made with small barbs on the sides near the bottom end as shown to assist retention.
The neck/fingerboard 10 is typically made of hardwood in quality instruments, and conventional frets 12A are typically made a soft malleable metal alloy such as German silver.
An example of such fret structure is found in U.S. Pat. No. 5,952,593 (FIG. 1A).
Such fret structure and mounting between parallel channel sidewalls fails to provide sufficient positive constraint to hold the fret 12A in place in the neck/fingerboard 10: instead, even with the barbs, the retention of the fret depends on friction deriving from the accuracy of a tight fit, which is subject to manufacturing tolerances and/or aging of the wood. Thus there is an inherent risk, borne out by actual experience, that in time, as the wood in the neck/fingerboard relaxes slightly, the frets can become loose and work upwardly out of place. This problem has been addressed by the use of adhesives and/or the addition of barbs on the tine portion in effort to improve the retention and the lifetime reliability.
The conventional cross-sectional shape of the upper exposed portion of the fret 12A has evolved to the convex top curvature shown, as part of the conventional overall fret structure and mounting system that has become commercially accepted as a practical tradeoff between the seven parameters described above.
Typically, there is deterioration of the frets after a certain amount of playing: the soft frets wear unevenly along the tip as a result of various expressive fingering techniques such as sliding up and down the fretboard and pitch bending by stretching strings sideways along the frets. This unevenness can be accommodated to some extent by resetting the action higher, i.e. relocating the strings further away from the fretboard: however this makes fingering and two-handed string tapping more difficult. Properly reconditioning the instrument for worn frets involves sanding and/or filing the frets down for overall leveling uniformity and, in a luthier""s operation known as crowning, re-rounding them as required to restore the original uniform playing action along the fretboard. Frets that are excessively worn or that have worked loose may have to be removed and replaced with new frets that, when installed, will need to be individually dressed.
FIG. 1B depicts a cylindrically-shaped fret 12B fitted into a channel of U-shaped cross-section machined into the neck/fingerboard 10 to provide an exposed arc that corresponds to the exposed fret portion shown in FIG. 1A, and can be inserted downwardly between the parallel portion of the channel sidewalls. An example of the structure shown in FIG. 1B is found in U.S. Pat. No. 4,633,754, granted to Chapman, the present inventor, wherein retention is provided by adhesive in the side gaps in the upper region of the U-shaped channel.
FIG. 1C depicts a cylindrical fret 12C that fits closely into a channel with a cross-section that has no parallel sidewalls; instead it is circular with a gap opening at the top that exposes the exposed arched portion of the fret 12C, which must be inserted endwise into the channel, providing positive fret retention against vertical shifting. Examples of such structure are found in U.S. Pat. No. 3,712,952 (FIG. 2) to Terlinde, British patent 1,394,346 (FIG. 2) to Wood, and in German patent 2,553,563 (FIG. 3) to Kist.
FIG. 1D depicts a version of FIG. 1C with the cylindrical fret 12D retained by flanking inter-fret spacers 10A that form a fingerboard surface layer attached onto neck 10, as in U.S. Pat. No. 4,633,754 by the present inventor.
FIG. 1E depicts a hollow tubular fret 12E in a close-fitting channel formed between inter-fret surface blocks 10Axe2x80x2 and retained by a screw traversing a full length support panel 10B fastened onto the main wooden portion of neck 10. An example of such structure is found in U.S. Pat. No. 4,221,151 (FIG. 2) to Barth.
FIG. 1F depicts a fret 12F of substantially triangular cross-sectional shape supported on a flat upper surface of neck 10 and retained in place by closely-fitting fingerboard spacer segments 10B. An example of such structure is found in U.S. Pat. No. 2,553,563 (FIG. 4) to Kist. The acute angle (60 degrees for an equilateral triangle) at the fret tip is found to detract from playing comfort due to excessive steepness of the two flat sidewalls.
FIG. 1G depicts a fret 12G having a generally half round cross-sectional shape retained in a close-fitting channel machined in the neck/fingerboard 10, as shown in British Patent 1,450,582 to Wood.
FIG. 1H depicts a fret 12H having a generally semi-elliptical or xe2x80x9cbulletxe2x80x9d cross-sectional shape, set in a close-fitting channel machined in neck/fingerboard 10. An example of such structure is found in U.S. Pat. No. 5,072,643 to Murata.
Frets of known art and their mountings such as those described above have been subject to one or more of the above described shortcomings or problems relating to the six parameters listed above.
It is noted that amongst the eight examples described above, only the conventional configuration in FIG. 1A fails to provide positive fret retention in the vertical direction: all of the others represent approaches to overcome this deficiency. Without special precautions or fixes, full round fret shapes such as in FIGS. 1B-1D are vulnerable to rotational shifting of the fret, and with the exception of FIG. 1E, all others shown are vulnerable to longitudinal shifting.
To produce a high quality stringed instrument, even though the retaining channels are machined into the neck/fingerboard as accurately as possible, it has been found necessary to dress the fret tips by sanding and/or filing after installation on the fretboard, so as to align the fret tips in a level plane to obtain the optimal string interface relationship for good playing action, and to then crown the frets as needed.
When the shape of the fret tip is inherently convex as in FIGS. 1A-E, 1G and 1H, such fret optimization is difficult and time-consuming due to the large amount of fret material that must be removed initially to accomplish proper leveling. Furthermore, some frets may be left with an excessively wide flat surface at the fret tip, which must then be individually crowned to preserve pitch accuracy and uniform feel to the fingers.
In contrast to the foregoing common luthier""s challenges, excessively steep surfaces on both sides of the fret such as in FIG. 1F, where the angle formed is acute, i.e. less than 90 degrees (60 degrees for an equilateral triangle), tend to detract is from the playing xe2x80x9cfeelxe2x80x9d of the instrument, typically causing bumpy obstructions to expressive finger sliding techniques. As an extreme example in this direction, retractable frets having a rectangular cross-sectional shape with vertical sidewalls are disclosed in U.S. Pat. No. 4,722,260 to Pigozzi.
It is a primary object of the present invention to provide an improved fret configuration and mounting system for stringed instruments that facilitates individual dressing of the fret tips, which includes leveling and rounding, thus enhancing the performance of music by providing accurate uniform alignment of all fret tips in a flat plane close to the strings,
It is an object to configure the fret with a cross-sectional exposed shape that will be judged by players to have a superior tactile xe2x80x9cfeelxe2x80x9d when playing the instrument, including the sensation of greater space for the fingers between the frets.
It is an object to configure and implement the fret and its mounting system in a manner that will benefit the aesthetics and overall appearance of the instrument.
It is an object to configure the fret and its mounting system in a manner that enhances producibility including ease of assembly, overall fret tip leveling and individual fret tip dressing.
It is an object to configure the fret and its mounting system in a manner that keeps flat surfaces at fret tips narrow so as preserve pitch accuracy.
It is an object to make the cross-sectional shape of the frets such that they can be fabricated from stock material in a standard form that is readily available.
It is an object to configure the fret and its mounting system to provide superior long-term reliability, including stability and durability, particularly with regard to fret retention in the neck/fingerboard over a period of years.
It is a further object to provide a fret configuration that is readily maintainable with regard to field refurbishment, adjustment and replacement.
It is a further object to provide a fret retaining system that allows latitude in designating fret height without sacrificing anchoring integrity.
The above mentioned objects have been satisfied in the present invention of a novel fret configuration that utilizes standard square metal stock, preferably of stainless steel, typically {fraction (3/16)} inch square, oriented such that the two cross-sectional diagonals are respectively substantially parallel and perpendicular to the fingerboard surface, thus making the fret tip the apex of a 90 degree angle.
Compared to lesser or greater angles, the 90 degree angle at the top corner of the square fret of the present invention has been found to be beneficial both for the xe2x80x9cfeelxe2x80x9d of playing the instrument and for ease of manufacture, and can be retained reliably in channels machined in the neck/fingerboard with a shape that fits the fret closely and provides optimal fret exposure, locating the horizontally diagonal corners beneath the fingerboard surface, positively constrained against upward shifting, by 45 degree inclined channel sidewalls.
The frets, when assembled in place, are readily dressed preferably with a belt sander or file, to accurately level off the fret tips to an even plane for uniform close relationship with the strings. This leaves a flat surface on each fret tip of varying width, but, due to the 90 degree angle, these widths are close to uniform and always narrow enough, typically in the range of a few thousandths of an inch, that pitch is not compromised.
Each fret is then further dressed individually to smoothly round the corners at the edges of the flat surface and thus further improves the playing feel, particularly on those stringed instruments that are intended for the two-handed tapping technique, such as the Chapman Stick product line. Such dressing can often be done in the final polishing process with a hand-held rotary sander.
The nominal 90 degree angle of the square-shaped fret rods has been found to facilitate these manufacturing operations in comparison to the rounded contour presented by frets of known art with convex shapes including conventional (FIG. 1A), round (FIGS. 1B-1E), half round (FIG. 1G) and semi-elliptical (FIG. 1H).
The nominal 90 degree angle has also been found to improve playability in comparison to more acute angles such as 60 degrees as shown in FIG. 1F.
The bottom corner opposite the fret tip may be optionally machined to remove material since the shape there is non-critical. A preferred five-faceted embodiment is made to have a flat bottom facet 0.15 inch wide: this provides the fret with good base support when the channel is shaped to closely fit the fret, and preserves neck strength by permitting shallower channel cuts.